Handling of liquid samples, reagents, and possibly other process fluids is essential for the implementation of automated clinical chemistry test methods. Conventionally, liquid samples, process fluids (e.g., purified water), and liquid reagents are aspirated and dispensed within an automated clinical analyzer by using a probe. In certain clinical analyzer instruments used to test for the presence of an analyte or other component in a biological fluid sample (otherwise referred to as “specimens”), it may be desirable to precisely meter one or more liquid reagents in the process. For example, in some automated testing systems (e.g., clinical analyzer instruments), a portion of a specimen contained in a sample container (such as a test tube, sample cup, vial, and the like) may be aspirated into a reaction vessel (e.g., a cuvette) in order to determine a presence of a particular analyte or component substance contained therein. As part of this process, precise metering of one or more liquid reagents into the reaction vessel along with the specimen portion may be accomplished. It is desired that during the metering process, the liquid reagent and the sample be mixed in order to provide a homogeneous mixture. In some testing methods, other process fluid (e.g., purified water) may also be added.
A conventional probe configuration used for aspiration includes a probe having a relatively small outer diameter. The probe may be coupled to a section of tubing that is, in turn, coupled to a pump (e.g., a piston pump). The aspiration system, including the probe and the pump, is typically primed with purified water.
Liquid reagents are often contained in a reagent container having a plurality of compartments. Some liquid reagents may include particles contained within a carrying liquid, and such particulates may settle over time. Accordingly, a mixing process onboard the automated clinical analyzer may be used to re-suspend these settled particulates into a homogeneous suspension of particles before they are aspirated and dispensed into a reaction vessel. Conventional mixing methods include (1) ultrasonic mixing and (2) aspiration and dispensing of a relatively large volume of the liquid reagent. Undesirably, the ultrasonic mixing method may cause damage to certain particulate reagents. Moreover, a prior art aspiration and dispense method (also referred to as the “sip-and-spit method”) includes aspirating into the probe and the tube a relatively large volume of reagent (e.g., about 50% or more of the volume of the liquid reagent) from a particular reagent container and then dispensing the liquid reagent back into the particular reagent container one time. Such sip-and-spit methods may be inefficient at promoting or maintaining mixing of the particulate with the reagent carrier liquid, and may cause other problems.
Accordingly, methods and systems that may improve mixing of liquid reagent including particulates are desired.